The propagation of microbial cells to obtain either fermentation products or to recover cell protein or both is well known. Furthermore, processes for the propagation of microbial cells in a medium containing hydrocarbons as the main assimilable carbon source are also known.
There is considerable interest in fermentation processes which can use as the fermentation substrate simple hydrocarbons and other inexpensive carbonaceous materials, such as methanol, synthesis gas (H.sub.2 and CO), or a mixture of CO.sub.2 and H.sub.2 which would normally be flared or otherwise disposed of in petroleum refining.
The use of methanol as the main source of assimilable carbon in such fermentation processes is particularly attractive because of the advantages it offers. Methanol has the advantage of being miscible with water; it can be easily and cheaply produced from a wide range of hydrocarbon materials; it can be easily produced in virtually any area of the world having any form of fossil fuel supplies and it is characterized by the absence of potentially carcinogenic polycyclic hydrocarbons.
In the past, attempts to grow microbial cells using methanol as the main assimilable carbon source have not been particularly successful. The ability of microorganisms to grow on single carbon compounds, especially those that contain methyl groups, appears restricted to a specialized metabolic group known as methylotrophs. By and large, most of what is known about methyltrophic bacteria is limited to obligately aerobic species that generally contain novel pathways foe one-carbon metabolism (1). More recently, studies on one-carbon metabolism in anaerobic methanogens have demonstrated that these bacteria can grow on either CH.sub.3 OH, H.sub.2 /CO.sub.2, CO, or methylamine as sole sources of carbon and energy (2, 3, 4, 5). Several species of anaerobic acidogenic bacteria have been described that can grow on H.sub.2 /CO.sub.2 or formate as sole carbon and energy sources (6,7) or that contain unique one-carbon metabolism reactions for homoacetic acid fermentations of multicarbon compounds (8,9).
In the past, Methanosarcina barkeri was the only described obligately anaerobic bacterium known to be capable of utilizing methanol and other one carbon compounds as the sole source of energy for growth.
The development of a process for the biological conversion of coal or biomass pyrolysis products (e.g. H.sub.2, CO.sub.2, CO and CH.sub.3 OH) to multicarbon atoms would be valuable as it would allow the further development of processes for chemical feed stock production.